JPS63285623A - Position detector - Google Patents

Abstract

PURPOSE:To detect a position designated by a cordless position indicator with high accuracy by detecting the phase of the inductive voltage produced at a loop coil as well as the phase produced when an AC signal is sent directly to a receiving circuit and to detect the phase difference of a turning circuit from those detected phases. CONSTITUTION:When a pen 4 is operated on a position detecting part 1, a current flowing through a tuning circuit 41 has a phase difference in accordance with the state of the part 1 set at that time point against the voltage. Thus the phase of the inductive voltage produced at the loop coils 11-1-11-48 is set at the value equal to the sum of the phase set based on the phase difference between the voltage and the current of the circuit 41 and the phase variance of a receiving circuit 6. The phase variance is detected when an AC signal is sent directly to the circuit 6 and subtracted from the phase of the inductive voltage produced at the coils 11-1-11-48 for detection of the phase of the inductive voltage, i.e., the phase difference between the voltage and the current of the circuit 41. Then the state of the indicator 1 is identified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position detection device that can detect the designated position of a cordless position indicator and identify its state.

(Prior Art) As a conventional position detection device, a pulse current is applied to a drive coil provided at one end of a magnetostrictive transmission medium or a tip of a position indicator, and magnetostrictive vibration waves are generated in the magnetostrictive transmission medium. , a processing device or the like measures the time until an induced voltage based on the magnetostrictive oscillation waves is detected in a detection coil provided at the tip of the position indicator or one end of the magnetostrictive transmission medium, and calculates the designated position of the position indicator from this. There was something I was jealous of.

In addition, as other conventional position detection devices, a plurality of drive lines and detection lines are arranged perpendicularly to each other, and a current is sequentially passed through the drive lines and the detection lines are sequentially selected to detect the induced voltage. There is a device in which a position specified by a position indicator having a magnetic material such as the above is detected from the position of a detection line where a large induced voltage is induced.

(Problem to be solved by the invention) Although the former device has relatively good position detection accuracy, it requires a code between the position indicator and the processing device to send and receive timing signals, etc. Handling is severely restricted and the position indicator must be held perpendicular to the magnetostrictive transmission medium and used in close proximity.

In addition, although the position indicator can be made cordless in the latter device, the resolution of the coordinate position is determined by the line spacing,
If the distance between the lines is reduced in order to increase the resolution, the signal-to-noise ratio and stability will deteriorate, and therefore it is difficult to increase the resolution, and it is also difficult to detect the position directly above the intersection of the drive line and the detection line. Furthermore, the position indicator had to be placed very close to the line.

In addition, in any of the above-mentioned devices, in order to transmit the status of switches, etc. in the position indicator to the processing device side, a code other than the one for position detection or a transmitter/receiver of wireless signals such as ultrasonic waves or infrared rays is required. The problem was that it was necessary.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device that has good operability because the position indicator is not connected anywhere, is capable of highly accurate position detection, and can identify the state of the position indicator.

(Means for Solving the Problems) In order to solve the above-mentioned problems, as a first invention, there is provided a position detection unit including a large number of loop coils arranged in parallel in the position detection direction;
a selection circuit that sequentially selects one loop coil from the plurality of loop coils; a transmission circuit that drives the selected one loop coil with an alternating current signal of a predetermined frequency; and a filter and a capacitor; a position indicator having a tuning circuit in which the tuning frequency is set to be a tuning frequency, and the phase difference between the voltage and the current can be changed according to the state; a receiving circuit that detects induced voltages of approximately the same frequency; a transmission/reception switching circuit that alternately connects the selected one loop coil to the transmitting circuit and the receiving circuit; and a position indication based on the induced voltage generated in each loop coil. At the same time as calculating the specified position of the position indicator, the phase is detected, and the phase when the AC signal is sent directly to the receiving circuit is detected. From these, the phase difference of the tuned circuit is detected, and the position indicator is detected. The present invention proposes a position detection device comprising a processing device configured to identify a state, and as a second invention, a position detection device in the X direction and Y direction formed by arranging a large number of loop coils in parallel in the X direction and Y direction, respectively. a detection unit, an X-direction and Y-direction selection circuit that sequentially selects one loop coil in the X-direction and Y-direction from the plurality of loop coils in the X-direction and Y-direction, and the selected X-direction and Y-direction. It includes a transmission circuit that drives one loop coil with an alternating current signal of a predetermined frequency, a coil and a capacitor, the predetermined frequency is a tuning frequency, and the phase difference between voltage and current can be changed according to the state. a position indicator having a tuned circuit configured to
During the voltage generated in one loop coil in the direction and Y direction,
a receiving circuit that detects an induced voltage having a frequency substantially the same as the predetermined frequency; and a receiving circuit that alternately connects one of the selected loop coils in the X and Y directions to the transmitting circuit and the receiving circuit. Transmission/reception switching circuit, X direction and Y direction
The specified position of the position indicator in the X direction and Y direction is calculated from the induced voltage generated in each loop coil in the direction, and the phase thereof is detected, and the phase when the AC signal is directly sent to the receiving circuit. The present invention proposes a position detecting device comprising a processing device that detects the phase difference of the tuned circuit and identifies the state of the position indicator.

(Function) According to the first invention, one of the many loop coils is selected by the selection circuit, the transmission circuit is connected to it by the transmission/reception switching circuit, and an alternating current signal of a predetermined frequency is applied. Then, radio waves are generated from the loop coil. The radio wave excites a coil in a tuned circuit of a position indicator that specifies a position on the position detecting section, and causes the tuned circuit to generate an induced voltage synchronized with the alternating current signal. Thereafter, when a receiving circuit is connected to the selected one loop coil by the transmission/reception switching circuit and the AC signal is cut off, the radio wave disappears, but the induced voltage generated in the tuned circuit of the position indicator remains in the selected loop coil. As the current flows through the circuit, it gradually attenuates based on internal losses. The current flowing through the tuned circuit causes the coil in the tuned circuit to generate radio waves having approximately the same frequency as the frequency of the alternating current signal applied to the first loop coil.

Since the radio waves reversely excite the first loop coil connected to the receiving circuit, an induced voltage is generated in the first loop coil that has approximately the same frequency as the frequency of the alternating current signal and gradually attenuates. Transmission and reception of the radio waves is repeated sequentially by switching the loop coil, and is performed by resonance between the loop coil and the coil of the position indicator, so the shorter the distance between the loop coil and the coil of the position indicator, the greater the induced voltage. The voltage value of increases. Therefore, the induced voltage generated in the loop coil closest to the position where the position indicator is placed (designated position) is the maximum, and the induced voltage that gradually decreases as the distance from the designated position increases is generated in each loop coil. The voltage value of each of the induced voltages is processed by a processing device, and the coordinate values of the position where the voltage value becomes the maximum value, that is, the designated position of the position indicator, are determined.

Note that even if the position indicator is moved along the direction perpendicular to the position detection direction, the distance between each loop coil and the position indicator does not change, so the same coordinate values can be obtained.

On the other hand, the current flowing through the tuned circuit flows with a phase difference corresponding to the state of the position indicator at that time with respect to the voltage, and the phase of the induced voltage induced in one loop coil is the phase difference between the voltage and current in the tuned circuit. This is the phase based on the phase difference plus the phase shift in the receiving circuit. The phase shift is detected when an alternating current signal is directly sent to the receiving circuit, and by subtracting this phase shift from the phase of the induced voltage induced in the first loop coil, the phase of the induced voltage is calculated. In other words, the phase difference between voltage and current in the tuned circuit is detected and the state of the position indicator is identified.

Further, according to the second invention, in the X direction and the Y direction,
The induced voltage based on the resonance between the loop coil and the coil of the position indicator is determined, and from this the coordinate values of the so-called two-dimensional specified position of the position indicator in the X direction and Y direction are determined, and as described above, The status of the position indicator is classified by job.

(Embodiment) Fig. 1 shows a first embodiment of the position detection device of the present invention, in which 1 is a position detection section, 2 is a selection circuit, 3 is a transmission/reception switching circuit, and 4 is a position indicator. , 5 is a transmitting circuit, 6 is a receiving circuit 1, and 7 is a processing device.

The position detection unit 1 includes a large number, for example, 48 loop coils 11-1, 11-2, and 11-2, each having conductors parallel to each other.・・・・・・
. . 11-48 are arranged in parallel in the direction of arrow A (hereinafter referred to as position detection direction) in the figure. Further, the loop coils 11-1 to 11-48 are arranged parallel to each other and overlapping each other. Although each of the loop coils 11-1 to 11-48 is configured with one turn here, it may be configured with multiple turns if necessary. The position detection section 1
For example, a large number of loop coils can be used by connecting a large number of parallel conductors formed by etching a well-known printed circuit board with jumper wires or the like.

The selection circuit 2 includes the plurality of loop coils 11-1 to 11.
One end of the loop coils 11-1 to 11-48 is connected to one terminal group 21, and the other end is connected to another terminal group 22, respectively. It is connected. A selection contact 23 corresponding to the terminal group 21 and a selection contact 24 corresponding to the terminal group 22
are interlocked with each other, operate based on information from the processing device 7, and select one loop coil. The selection circuit 2 is realized by combining a large number of well-known multiplexers.

The transmission/reception switching circuit 3 alternately connects one loop coil selected by the selection circuit 2 to the transmission circuit 5 and the reception circuit 6, and the selection contact 23 of the selection circuit 2
and 24 are connected to selection contacts 31 and 32, respectively. Further, the two output terminals of the transmitting circuit 5 are terminals 33
．． 35, and the two input terminals of the receiving circuit 6 are connected to terminals 34, 36. Said terminal 33°3
The selection contact 31 corresponding to terminal 4 and the selection contact 32 corresponding to terminal 35 and 36 are interlocked with each other and operate based on a transmission/reception switching signal, which will be described later, to switch between transmission and reception. Note that the transmission/reception switching circuit 3 is also realized by a well-known multiplexer.

The position indicator 4 is a stylus pen (hereinafter simply referred to as a pen), and has a built-in tuning circuit 41 including a coil and a capacitor.

FIG. 2 shows the detailed structure of Ben 4, in which a core 43 of a ballpoint pen or the like is slid into a pen shaft 42 made of a non-metallic material such as synthetic resin from near the tip. A ferrite core 44 with a through hole that can be freely accommodated, a coil spring 45, and a switch 411. Ferrite core 44
A coil 412. A tuning circuit 41 consisting of capacitors 413 and 414 is integrated and built in, and a cap 46 is attached to the rear end.

As shown in FIG. 3, the coil 412 and capacitor 413 are connected in series to form a well-known resonant circuit.
The numerical value 3 is set to a value such that the phases of the voltage and current resonate (synchronize) in the same phase at a predetermined frequency fO. Further, a capacitor 414 is connected in parallel to both ends of the capacitor 413 via a switch 411.
11 is turned on, the phase of the current in the above-mentioned resonant circuit is delayed by a predetermined angle, and the phase of the received signal, which will be described later, is
For example, the switch 4 is delayed by 45 inches.
11 holds the pen shaft 42 by hand or the like, and when the tip of the core body 43 is pushed into the pen shaft 42 by pressing it against the input surface (not shown) of the position detection unit 1, the coil spring 45 is activated by the rear end. It is turned on by being pressed through the switch.

FIG. 3 shows the details of the tuning circuit 41, the transmitting circuit 5, and the receiving circuit 6, as well as the overall configuration of the device. In the figure, 51 is a timing circuit, 52 is a low-pass filter (LPF), and 53
is a drive circuit, these constitute the transmission circuit 5, 61 is an amplifier, 62 is a reception timing switching circuit, 63
is a bandpass filter (BPF), 64 is a detector, 65.66
is a phase detector (PSD), and 67, 68, and 69 are low-pass filters (LPF), which constitute the receiving circuit 6.

The processing device 7 is composed of a well-known microprocessor, etc., and controls the timing circuit 51 and also controls the position detection section 1.
It also controls the switching of each loop coil of the
D) Convert and execute arithmetic processing to be described later to calculate the coordinate values of the position designated by Ben 4, identify the state of the switch, etc., and perform processing in accordance with this.

Next, the operation will be described. First, the manner in which radio waves are transmitted and received between the position detecting section 1 and the pen 4, and the signals that are removed will be described with reference to FIG.

The timing circuit 51 has a predetermined frequency fO1, for example, 500.
kHz rectangular wave signal A1 The phase of the rectangular wave signal A is 90''
Delayed signal B1 predetermined frequency fk, for example 15.62
Generates a 5kHz transmission/reception switching signal C and reception timing signal. The rectangular wave signal A is sent to a phase detector 65 and is converted into a sine wave signal E by a low-pass filter 52 and sent to a drive circuit 53 and a reception timing switching circuit 6.
Furthermore, the rectangular wave signal B is sent to the phase detector 66, the transmission/reception switching signal C is sent to the transmission/reception switching circuit 3, and the reception timing signal is sent to the reception timing switching circuit 62. be done.

The sine wave signal E is converted into a balanced signal by the drive circuit 53, and is further sent to the transmission/reception switching circuit 3. The transmission/reception switching circuit 3 selects one of the driving circuit 53 and the amplifier 61 based on the transmission/reception switching signal C. In order to switch and connect one side, the signal output from the transmission/reception switching circuit 3 to the selection circuit 2 takes a time T(-1
/2fk), here 500kH2 every 32:gsec
This becomes a signal F that may or may not emit a signal.

The signal F is passed through the selection circuit 2 to the first loop coil 11-i (i-1, 2,...4) of the position detection section 1.
8), but at this time, the loop coils 11 to i
generates radio waves based on the signal F.

At this time, if the pen 4 is held in a substantially upright state, that is, in a used state, near the loop coil 11-1 of the position detection unit 1, the radio wave excites the coil 412 of the pen 4, and the tuning circuit 41 of the pen 4 excites the pen 4. An induced voltage G synchronized with the signal F is generated.

Thereafter, when the loop coil 11-1 is switched to the receiving circuit 6 side as the signal F enters a no-signal period, that is, the receiving period, the radio wave from the loop coil 11-1 immediately disappears, but the induced voltage G gradually attenuates depending on the loss within the tuning circuit 41.

On the other hand, the current flowing through the tuned circuit 41 based on the induced voltage G causes the coil 412 to emit radio waves. Since the radio waves reversely excite the loop coil 11-1 connected to the receiving circuit 6, the loop coil 11-1 includes a coil 412.
An induced voltage is generated by radio waves from the The induced voltage is sent from the transmission/reception switching circuit 3 to the amplifier 61 only during the reception period, is amplified, becomes a reception signal H, and is further sent to the reception timing switching circuit 62.

The reception timing switching circuit 62 is for sending either the aforementioned sine wave signal (calibration signal) E or the reception signal H to the bandpass filter 63, and the period when the reception timing signal is high (H) is Outputs the signal selected from the sine wave signal E or the received signal H based on the calibration signal/received signal (S/R) selection signal supplied from the processing device 7, and what is the low (L) level period? is also not output.

Note that the reception timing signal is essentially the transmission/reception switching signal C.
This is the inverted signal of Further, as the S/R selection signal, only the selection signal of the reception signal is input to the reception timing switching circuit 62 during the period when position detection is being performed.
During the state identification period, the reception signal selection signal and the calibration signal selection signal are transmitted every time the reception timing signal repeats high/low, that is, transmission and reception are repeated a predetermined number of times, for example, seven consecutive times. It is switched and input.

Assuming that the selection signal of the reception signal among the S/R selection signals is input to the reception timing switching circuit 62, a signal I (substantially the same as the reception signal H) is obtained as an output. The signal l is sent to a bandpass filter 63,
The bandpass filter 63 is a filter having a passband centered at the frequency fO, and the signal ! A signal J (strictly speaking, in a state in which several signals (2) are inputted to the bandpass filter 63 and converged) having an amplitude corresponding to the energy of the acid component at a frequency fO in the middle is passed through a wave detector 64 and a phase detector 6'5.
66.

The signal J input to the detector 64 is detected and rectified,
After being converted into a signal, it is converted into a DC signal having a voltage value corresponding to approximately 1/2 of the amplitude of the signal J, for example, VX, by a low-pass filter 67 with a sufficiently low cutoff frequency, and sent to the processing device 7. be done.

The voltage value Vx of the signal is between Ben 4 and the loop coil 11-.
The loop coil 1 shows a value proportional to the distance between the loop coil 1 and
1-1 changes when switched, so by converting the voltage value Vx obtained for each loop coil into a digital value and performing the arithmetic processing described below on these values, the coordinate values of the specified position by Ben 4 are calculated. be done.

On the other hand, the rectangular wave signals A and B are input to the phase detectors 65 and 66 as detection signals, and at this time, the signal J
Assuming that the phase of the square wave signal A almost matches that of the rectangular wave signal A, the phase detector 65 outputs a signal Ml (substantially the same as the signal) which is the positive inversion of the signal J, and the phase The detector 66 outputs a signal M2 having a symmetrical waveform on the positive and negative sides.

The signal M1 is passed through the same low-pass filter 68 as the signal J.
The signal M2 is converted into a DC signal Nl (substantially the same as the signal) having a voltage value corresponding to approximately 1/2 of the amplitude of Vx, and sent to the processing device 7. The signal M2 from the phase detector 66 is converted into a DC signal N2 and sent to the processing device 7. However, since the positive and negative components of the signal M2 from the phase detector 66 are the same, the voltage value of the output from the low-pass filter 69 is It becomes 0 [v].

The processing device 7 A/D converts the output values of the low-pass filters 68 and 69, here the signals Nl and N2, and further uses these digital values to perform arithmetic processing according to the following equation (1),
The phase difference θ between the signals applied to the phase detectors 65 and 66, here J and the rectangular wave signal A, is calculated.

θ--'tan (VQ /VP) -・
(1) Here, vP represents a digital value corresponding to the output of the low-pass filter 68, and vQ represents a digital value corresponding to the output of the low-pass filter 69.For example, in the case of the signal J described above, the signal The voltage value of N1 is VX, but the voltage value of signal N2 is 0 [V], that is, VQ-0, so the phase difference is θ-θ°.

Incidentally, a ceramic filter with a mechanical vibration component is used as the bandpass filter 63, but its vibration frequency changes slightly with changes in the surrounding temperature, and the signal input to the filter and the filter This may cause a phase change between the output signal and the output signal. For this reason, the phases of the above-mentioned received signal H (or signal There is no guarantee that the phase difference with the wave signal A, in other words, the phase difference between the voltage and current in the tuned circuit 41 is directly represented.
Although the phase difference between the received signal H (or signal ■) and the rectangular wave signal A and the phase difference between the voltage and current in the tuning circuit 41 are not the same except in the case of θ'', they are in a fixed constant relationship.

).

On the other hand, when the selection signal of the calibration signal among the S/R selection signals is input to the reception multi-timing switching circuit 62, the signal corresponding to the part corresponding to the reception period of the sine wave signal E is output. E- is obtained. The signal E' is converted by a bandpass filter 63 into a signal having a waveform similar to that of the signal J (however, the amplitude and one phase are not necessarily the same), and further passed through a phase detector 65, 66 and a low-pass filter 68.゜69
The signal is then sent to the processing device 7, where it undergoes the same processing as described above, and the phase difference θ is calculated.

The signal E' is a part of the sine wave signal E obtained by passing the rectangular wave signal A through the low-pass filter 52, and is considered to always be in the same phase as the rectangular wave signal A. The phase difference θ obtained in the device 7 represents the phase shift between the signal input to the bandpass filter 63 and the signal output from the bandpass filter 63.

Therefore, when the received signal H (or I) is sent to the bandpass filter 63, that is, when the processing device 7 is sending out the selection signal of the received signal among the S/R selection signals, the phase difference obtained is θr. The phase difference obtained when the signal E' is sent to the bandpass filter 63, that is, when the processing device 7 is sending out the selection signal of the calibration signal among the S/R selection signals, is θS.
In this case, by subtracting the phase difference θS from the phase difference θ′ as shown in equation (2) below, the influence of the phase shift in the bandpass filter 63 is canceled, and the received signal H(
Alternatively, the true phase difference θo1 between the signal I) and the rectangular wave signal A, that is, the phase difference between the voltage and current in the tuning circuit 41 can be determined.

θ0−θr−θS ・・・・・・(2
) Figure 5 shows the relationship between the aforementioned phase differences θ', θS, and θ0. Figure 5(a) shows the relationship between the phase differences θ', θS, and θ0. An example will be shown in which the phase difference θr and 00 are equal. In addition, FIG. 5(b) shows that due to changes in ambient temperature, etc., the bandpass filter 6
An example is shown in which a phase shift occurs in 3. In this case, the phase difference θ' is expressed as the sum of θS and 00.
Although FIG. 5(b) shows an example where a delayed phase occurs as a phase shift, the above relationship is the same even when an advanced phase occurs.

In the above example, if the phase difference is θ5-06, the phase difference between the received signal H (or signal l) and the rectangular wave signal A is θ0-
Since θr-0', it can be seen that the voltage and current in the tuned circuit 41 are in phase, and the switch 411 is in the off state.

Further, the processing device 7 switches the reception timing switching circuit 62 to
When inputting the selection signal of the received signal among the R selection signals, the phase is 45'' from the signal J from the bandpass filter 63.
If the delayed signal J' is output, the signal J' is sent to the phase detectors 65 and 66 as before, and the signal Ml
' and M2°, but since the ratio of the positive side and negative side components in the signal M1° is equal to the ratio of the positive side and negative side components in the signal M2', the signals M1' and M2° are low. In the band pass filters 68 and 69, signals Nl' and N2'' having the same voltage value, for example, VX' are output to the processing device 7.

Similarly to the above, the processing device 7 converts the signals Nl' and N2° into A/D
The signal N1 is converted and the calculation process of equation (1) is performed.
The voltage values of ° and N2° are both VX', and VP-VQ
Therefore, the phase difference is θr−45′. Further, the processing device 7 switches the reception timing switching circuit 62 to receive timing switching circuit 62 as described above.
The selection signal of the calibration signal among the R selection signals is input to find the phase difference θS. If the phase difference θs-0', then the phase difference between the received signal and the rectangular wave signal A at this time θ0-θr-- 4
5', the phase of the current in the tuned circuit 41 lags the phase of the voltage by the predetermined angle, and the switch 4
It can be seen that 11 is in the on state.

In this way, the processing device 7 outputs the selection signal of the received signal and the selection signal of the calibration signal alternately, and calculates the phase difference θr from the output values of the low-pass filters 68 and 69 when the selection signal of the received signal is sent out. In addition, the phase difference θS is calculated from the output values of the low-pass filters 68 and 69 when the selection signal of the calibration signal is sent out, and by calculating the difference between the phase difference θ and θS, the received signal and Phase difference θo1 with square wave signal A
That is, the phase difference between the voltage and current in the tuned circuit 41 can be detected accurately, and whether the switch 411 is on or off can be accurately determined.

Note that the information indicating the on or off state of the switch 411 identified here is used as information for specifying the value to be actually input among the coordinate values of the position specified by Ben 4.

Next, with reference to FIGS. 6 to 8, position detection and identification of the state of the pen 4, here the on/off state of the switch 411, in the apparatus of the present invention will be explained.

First, when the entire device is powered on and enters the measurement start state, the processing device 7 sends a selection signal of the received signal from among the S/R selection signals described above to the reception timing switching circuit 62, and also sends the selection signal to the reception timing switching circuit 62. loop coil 11-1~1
1-48, information for selecting the first loop coil 11-1 is sent to the selection circuit 2, and the loop coil 1 knee 1 is connected to the transmission/reception switching circuit 3. The transmission/reception switching circuit 3 controls switching of the loop coil 11-1 alternately to the transmission circuit 5 and the reception circuit 6 based on the transmission/reception switching signal C mentioned above.

At this time, the transmitting circuit 5 transmits 16 500 kHz sine wave signals as shown in FIG. 6(a) (only 5 of them are shown in FIG. ) is sent to the loop coil 11-1. The switching between transmission and reception is repeated seven times for one loop coil, here 11-1, as shown in FIG. 6(b).

These seven transmission and reception repetition periods correspond to one loop coil selection period (448 μsec).

The output of the reception timing switching circuit 62 of the reception circuit 6 includes:
An induced voltage is obtained for one loop coil every seven reception periods, and as described above, this induced voltage is averaged by the bandpass filter 63, and then passed through the wave detector 64 and the phase detector 65.
．． 66 and low-pass filters 67 to 69 before being sent to the processing device 7.

At this time, the output value of the low-pass filter 67 is A/D converted,
A detected voltage proportional to the distance between Ben 4 and the loop coil 11-1 is temporarily stored as, for example, Vxl (actually, the output values of the low-pass filters 68 and 69 are also A/D converted, but at this point values are not accepted).

Next, the processing device 7 sends information for selecting the loop coil 11-2 to the selection circuit 2, connects the loop coil 11-2 to the transmission/reception switching circuit 3, and connects the loop coil 11-2 to the transmission/reception switching circuit 3 in proportion to the distance between the Ben 4 and the loop coil 11-2. Then, the loop coils 11-3 to 11-48 are sequentially connected to the transmission/reception switching circuit 3 in the same way, and the detection voltage VX2 is obtained and stored. Detection voltage Vx proportional to distance from Ben 4
1 to Vx4g (however, only a part of it is shown in an analog representation in FIG. 6(e)).

The actual detected voltage is obtained only in several loop coils in front and behind the position (xp) where Ben 4 is placed as the center, as shown in FIG.

When the voltage value of the stored detection voltage is above a certain detection level, the processing device 7 calculates coordinate values representing the specified position of the Ben 4 from these voltage values as described later.

Next, the processing device 7 operates the loop coils 11-1 to 11-.
48, detects the loop coil from which the maximum detected voltage is obtained, sends information for selecting this to the selection circuit 2, and also switches the reception timing of the selection signal of the reception signal among the S/R selection signals. The transmission and reception of the radio waves is repeated a plurality of times, for example, seven times, and at that time, the low-pass filter 6
The output values obtained from 8 and 69 are A/D converted, and the arithmetic processing of the above equation (1) is performed on them, and the phase difference θr
Calculate.

Further, the processing device 7 sends out a selection signal of the calibration signal among the S/R selection signals to the reception timing switching circuit 62 while keeping the loop coil from which the maximum detection voltage was obtained selected.
The transmission and reception of the radio waves (actually, the input of the sine wave signal E' to the reception timing switching circuit 62) is repeated a plurality of times, for example, seven times, and the output values obtained from the low-pass filters 68 and 69 are converted into A/ D transform and apply the above (
1) Execute the calculation process of the equation and calculate the phase difference θS.

Furthermore, the processing device 7 executes the arithmetic processing of equation (2), calculates the phase difference θ0 between the received signal and the rectangular wave signal A, detects the phase difference between the voltage and current in the tuning circuit 41, and switches the 411 on/off.

The identification result of whether the switch 411 is on or off is transferred to a host device (not shown) together with the coordinate values representing the specified position of the ben 4 described above.

When the first position detection and state identification are completed in this way, the processing device 7 performs the second and subsequent position detection as shown in FIG.
Out of the 48 loop coils, information for selecting only a certain number of loop coils, for example 10, before and after the loop coil from which the maximum detected voltage was obtained is sent to the selection circuit 2, and the output value is determined in the same manner as described above. Then, the position of Ben 4 is detected and the on/off state of the switch 411 is identified, and the obtained coordinate values and identification results are transferred and updated, and these steps are repeated.

Therefore, when Ben 4 is operated on the position detection unit 1, all the coordinate values of the specified position by Ben 4 are transferred to the host device, and at this time, when the switch 411 is turned on,
The on-state identification information is transferred to the higher-level device, and the higher-level device can recognize the coordinate values at this point as the coordinate values to be input.

In addition, in Fig. 8, level check means checking whether the maximum value of the detection voltage has reached the detection level and which loop coil has the maximum detection voltage, and checking whether the maximum value of the detection voltage has reached the detection level. If it has not been reached, subsequent coordinate calculations, etc. are stopped, and the center of the loop coil to be selected in the next position detection operation and state identification operation is set.

One method of calculating the coordinate value xp is to approximate the waveform near the maximum value of the detected voltages Vxl to Vx4g by an appropriate function, and calculate the coordinates of the maximum value of the function.

For example, in FIG. 6(C), the maximum detection voltage Vx3
By approximating the detection voltages Vx2 and Vx4 on both sides by a quadratic function, it can be calculated as follows (however, the coordinate values of the center positions of each loop coil 11-1 to 11-48 are x4g, and the interval is ΔX.)
. First, from each voltage and coordinate value, Vx2-a (x2-xp) +b ・-
-13) Vx3-a (x3-xp) +b
...i4) Vx4-a (x4-xp) +b
-...(5). Here, a and b are constants (a<0).

Also, x3−x2 =Δx −−(8)x
4-x2 = 2ΔX (7
). (8), (7) to (4), (5)
Substituting it into the formula and rearranging it, xp-x2+Δx/2 ((3Vx2-4 Vx3
+ Vx4) / (Vx2-2 Vx3+ Vx4)
)...(8) becomes.

Therefore, from each detection voltage Vxl to V x4g, extract the maximum detection voltage obtained at the time of the level check and the detection voltages before and after it, and extract these and the detection voltage of the loop coil from which the maximum detection voltage was obtained. The coordinate value xp of the specified position of the pen 4 can be calculated by performing an operation corresponding to the above-mentioned equation (8) from the coordinate value (known) of the previous loop coil.

FIG. 9 shows a second embodiment of the present invention, in which an example is shown in which position detection is performed in the X direction and the Y direction. That is,
In the figure, reference numeral 1a denotes a position detecting section in the X direction and the Y direction, which consists of two sets of the position detecting sections 1 in the first embodiment, superimposed so that their loop coils are orthogonal to each other. Further, 2a and 2b are selection circuits in the X direction and Y direction, 3a and 3b are transmission/reception switching circuits in the X direction and Y direction, 53a and 53b are drive circuits in the X direction and Y direction, and 61a and 61
Reference numerals b denote amplifiers in the X direction and in the Y direction, and each has the same configuration as the selection circuit 2, transmission/reception switching circuit 3, drive circuit 53, and amplifier 61 in the first embodiment.

Reference numeral 54 denotes an XY switching circuit, which applies a sine wave signal inputted from the timing circuit 51 via the low-pass filter 52 to either one of the drive circuits 53a or 53b to select the direction in which the position is to be detected. . Further, 62' is a reception timing switching circuit, which changes the reception signal from the amplifier 61a or the amplifier 61b or the sine wave signal from the low-pass filter 52 based on the position detection direction, the reception timing signal, and the S/R selection signal. , for selectively sending it to the bandpass filter 63. Further, 7a is a processing device, except that the processing device 7a controls the XY switching circuit 54 and the reception timing switching circuit 62' to perform position detection in the X direction and the Y direction alternately.
It is similar to

Incidentally, the timing of the second and subsequent position detection operations and state identification operations in the processing device 7a is shown in FIG.

As described above, according to this embodiment, the position (coordinates) of the pen 4 in two directions, the X direction and the Y direction, can be easily detected.

Note that the other configurations and operations are the same as those of the first embodiment.

In addition, in the first or second embodiment, by attaching a microphone or the like to the position detection unit 1 or 1a and providing the processing device 7 or 7a with a voice recognition function, various commands can be given by voice. You can also
In the second embodiment, the processing device 7a can be provided with a character recognition function and used as a tablet for inputting handwritten characters.

In addition, in the explanation so far, the phase difference between the voltage and current in the tuned circuit 41 is changed by turning on and off the switch 411, but the capacitor 4 of the tuned circuit 41
As 13, the phase difference can be changed by using an element whose capacitance value changes according to changes in the operating state of the pen 4, and the switch itself is not necessarily essential.

In addition, as the phase difference between the received signal and the rectangular wave signal A, two states were set: in-phase or delayed by 45 degrees, but the present invention is not limited to these, and there are many settings including a state where the phase is advanced. and can also identify them.

Further, the number of loop coils and the arrangement thereof in the embodiments are merely examples, and it goes without saying that the present invention is not limited thereto.

(Effects of the Invention) As explained above, according to the present invention, the loop coil of the position detection section has a tuning circuit that can set a predetermined frequency as the tuning frequency and change the phase difference between the voltage and the current according to the state. A radio wave is sent to the position indicator, and the loop coil receives the radio wave sent in the opposite direction from the tuned circuit, and at this time,
The generated induced voltage is detected, and this is applied to all of a large number of loop coils, and the specified position of the position indicator is detected from the obtained large number of induced voltages, and the phase of the reflected signal is detected. Since the phase when the AC signal is directly sent to the receiving circuit is detected, and the phase difference between the voltage and current in the tuned circuit is detected from this, even if a phase shift occurs in the receiving circuit, the tuned circuit can be The phase difference between the voltage and current at This eliminates the need for heavy parts such as batteries and magnets, and improves operability. In addition, since the position detection unit does not require any special parts, it can be applied to large-sized text boxes, electronic whiteboards, etc., and by increasing the accuracy of calculation processing for the obtained induced voltage, position detection accuracy can be improved. You can also increase it further. Further, if the position detection section is provided in the X direction and the Y direction, there are advantages such as position detection in two directions, the X direction and the Y direction.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing a first embodiment of the position detection device of the present invention, Fig. 2 is a sectional view of the stylus pen, and Fig. 3 is a detailed diagram of the tuning circuit, transmitting circuit, and receiving circuit of the stylus pen, as well as the device. A diagram showing the overall configuration, Figure 4 is a signal waveform diagram of each part of Figure 3, Figures 5 (a) and (b) are phase differences θr, θ
Diagram showing the relationship between S and θ0, Figure 6 (a) (b) (c
) is a timing diagram showing the basic position detection operation in the first embodiment, FIG. 7 is a diagram showing the detection voltage obtained from each loop coil during the first position detection operation, and FIG. 9 is a timing diagram showing the second and subsequent position detection operations and state identification operations, FIG. 9 is a diagram similar to FIG. 3 showing the second embodiment of the present invention, and FIG.
It is a figure similar to the figure. DESCRIPTION OF SYMBOLS 1... Position detection part, 11-1 to 11-48... Loop coil, 2... Selection circuit, 3... Transmission/reception switching circuit,
4... Stylus pen, 5... Transmission circuit, 6...
Receiving circuit, 7... Processing device, 41... Tuning circuit.

Claims (2)

[Claims] (1) A position detection unit including a large number of loop coils arranged in parallel in the position detection direction; a selection circuit that sequentially selects one loop coil from the large number of loop coils; and a predetermined selection circuit for the selected one loop coil. a transmitting circuit driven by an alternating current signal having a frequency of a receiving circuit for detecting an induced voltage having a frequency substantially the same as the predetermined frequency among the voltages generated in the selected one loop coil; A transmitting/receiving switching circuit alternately connected to the loop coil, and calculating the designated position of the position indicator from the induced voltage generated in each loop coil, detecting its phase, and directly transmitting the alternating current signal to the receiving circuit. detecting the phase of the tuned circuit, and detecting the phase difference of the tuned circuit from these;
A position detection device comprising a processing device configured to identify the state of a position indicator. (2) An X-direction and Y-direction position detection unit formed by arranging a large number of loop coils in parallel in the X-direction and a Y-direction, respectively; an X-direction and Y-direction selection circuit that sequentially selects one loop coil;
A transmission circuit that drives a loop coil in one direction with an alternating current signal of a predetermined frequency, and a transmitting circuit that includes a coil and a capacitor, the predetermined frequency is a tuning frequency, and the phase difference between voltage and current can be changed according to the state. a receiving circuit that detects an induced voltage having a frequency substantially the same as the predetermined frequency among the voltages generated in one of the selected loop coils in the X and Y directions; an X-direction and Y-direction transmission/reception switching circuit that alternately connects one selected loop coil in the X-direction and Y-direction to the transmitting circuit and the receiving circuit; and the induction generated in each of the X-direction and Y-direction loop coils. Calculating the specified position of the position indicator in the X and Y directions from the voltage, detecting the phase thereof, and further detecting the phase when the AC signal is directly sent to the receiving circuit,
and a processing device configured to detect the phase difference of the tuning circuit from these and identify the state of the position indicator.